So far the only new characters are Falcon and Winter Soldier, though the latter was technically in the last movie. Maybe Sharon Carter if the end female Shield Agent(Amanda Righetti) isn't her.

Returning characters?
Captain America
Nick Fury(most likely)

Those added up are 5 characters total.

Possible returning characters if story/script permits:
Red Skull(depending on if he really dissolved by the Cosmic Cube or was transported to another dimension; etc)
Arnim Zola(depending on how much inspiration they take from the comic for the character)